The action of a reflecting antenna

A historical survey of the literature dealing with the reflection of wireless waves reveals a difference of opinion concerning the phase-change produced when reflection takes place from Hertzian rod oscillators. In this paper the currents produced in two tuned vertical aerials both acting as receivers in a radiation field are discussed theoretically. Two special cases are considered in detail, viz. (1). when the aerials are less than one wavelength apart and are in line with the transmitter("end-on" position), and (2) when they are less than one wave-length apart and at right angles to the transmitter ("broadside-on" position). In the first case, the current in the aeiral nearer to the transmitter attains a maximum value when the distance D between the aerials is approximately 0.33¿ or 0.85¿, and is a minimum when D is approximately 0.60¿, where ¿ is the wave-length. The current in the aerial remote from the transmitter reaches a maximum value when D is 0.16¿, and then steadily decreases as the distance between the aerials increases to one wave-length. For the "broadside-on" position, the current in each aerial attains a maximum when the distance between teh aerials in 0.71¿. The details of the design of the short-wave oscillator and receiving aerials are outlined, and the method of procedure in order to obtain the current measurements is described. The experimental results obtained are compared with the theoretical calculations. The solutions of the general equation tan a(1 + cos ß) = (a2 ¿ 1)/a gives the critical values of the ratio of the distance between two tuned antennae to the length of the wave, for which the antenna currents are a maximum or a minimum, the plane of the antennae being at any angle ß to the direction of propagation.